The ballot measure will ask Californians to amend the state constitution to ban same-sex marriages in the wake of a state Supreme Court ruling last month allowing the civil unions to proceed. The new measure would trump the high court's ruling, The San Francisco Chronicle reported Tuesday.

Gay rights supporters said they will work hard to defeat the measure, which was officially placed on the Nov. 4 ballot Monday by California Secretary of State Debra Brown.

"We're not surprised by this at all and have been getting ready to run a very aggressive campaign," Steve Smith, a consultant to the Equality for All effort, told the newspaper. "This (initiative) asks California voters to take away a fundamental right from same-sex couples, and we don't believe they are willing to do that."

But there will be significant support for it, as well. The petition to put the constitutional measure on the ballot had 1.1 million signatures, and Proposition 22, a referendum opposing same-sex marriage that was struck down by the high court, passed with 61 percent of the vote.